Hi everyone,

I’ve been digging into an old Biostar A780L3B AM3 board and I’m trying to understand how the 95W CPU limit is handled in its BIOS.

There are older reports of this board warning on higher-TDP CPUs, but I wanted to look at the BIOS side more closely instead of stopping at the usual “don’t use anything over 95W” answer.

I’ve been comparing a couple of BIOS versions and looking at the relevant modules/strings. So far it seems the more interesting part is a threshold-related path rather than the old idea of just skipping the warning branch.

GitHub Link: A780l3B[125W]

Any feedback, contributions, or discussions are highly appreciated!

Thanks!

Edited June 23Jun 23 by DEADBYTE
IDK

Hello!

First of all, it's nice to see someone doing BIOS modding these days. But you jump over intermediate steps so it's hard to follow your mind.
What do you want to achieve in the end? Just to understand how the check works or patch it? This boards VRM is very weak and there's a reason this limitation has been implemented. Without mods and with medium o/c you're likely to burn it.
How do you find the needed section, hex editor and/or disassembler? How did you get a bad flash? Using standard methods I've always never seen a flash gone bad excluding cases when the flash itself was corrupted (they do die like other flash).

Hey Antinomy,

Fair points! Let me break it down for you:

1. What I wanted to achieve: To patch it and actually use it. I bought a 125W Phenom X4 955 by mistake and had zero budget for a new AM3 board. It was either mod the BIOS or let the CPU sit as a paperweight.

2. How I found it: Found the relevant AMI BIOS modules via MMTool/UBU, dropped them into a hex editor/disassembler, and tracked down the 95W limit threshold value. Modified the hex array from A0860100 to D0FB0100 to trick the power limit check to 130W.

3. The bad flash: That was just an initial experimental hiccup. It's fully fixed now.

And yes, I know the VRM on this Biostar is basically cardboard. I'm running it at bone-stock settings with direct fan cooling pointed straight at the VRM mosfets.

Currently typing this from the live Linux machine running this exact modded BIOS. All 4 cores running fine at 3200MHz, acpi_cpufreq is working perfectly. The ghetto setup lives!!